Add disallowPositionReuse

spec.bs

@@ -115,6 +115,7 @@ dictionary DocumentPictureInPictureOptions {
   [EnforceRange] unsigned long long width = 0;
   [EnforceRange] unsigned long long height = 0;
   boolean disallowReturnToOpener = false;
+  boolean preferInitialWindowPlacement = false;
 };
 
 [Exposed=Window, SecureContext]
@@ -219,6 +220,12 @@ problems.
         window such that the distance between the top and bottom edges of the
         viewport are |options|["{{DocumentPictureInPictureOptions/height}}"]
         pixels.
+
+If |options|["{{DocumentPictureInPictureOptions/preferInitialWindowPlacement}}"]
+exists and is true, then the user agent may use this hint to prefer behavior
+that is similar that is similar to steps 12 and 13, rather than considering any
+previous position or size of any previously closed |pip traversable| window.
+
 14. If |options|["{{DocumentPictureInPictureOptions/disallowReturnToOpener}}"] exists
     and is <code>true</code>, the user agent should not display UI affordances
     on the picture-in-picture window that allow the user to return to the
@@ -667,7 +674,32 @@ picture-in-picture experience. Use the
 button.
 
 <pre class="lang-javascript">
-documentPictureInPicture.requestWindow({ disallowReturnToOpener: true });
+await documentPictureInPicture.requestWindow({
+  disallowReturnToOpener: true
+});
+</pre>
+
+## Prefer initial window placement ## {#example-prefer-initial-window-placement}
+
+While a document picture-in-picture window is open, the user may manually
+resize or reposition it. If the document picture-in-picture window is closed,
+then reopened later, the user agent may use the previous position and size as
+a hint for where to place the new window rather than opening it in is original,
+default position.
+
+The site can provide a hint to the user agent that reusing the previous
+document picture-in-picture window position and size is not desirable
+by setting the {{DocumentPictureInPictureOptions/preferInitialWindowPlacement}}
+value to true.  For example, if the site is requesting the new document
+picture-in-picture window for an unrelated activity from the previous one, then
+the site might provide this hint to the user agent.  In response, the user
+agent may choose to use the default position, the default size, or the size
+hint provided by the site instead.
+
+<pre class="lang-javascript">
+await documentPictureInPicture.requestWindow({
+  preferInitialWindowPlacement: true
+});
 </pre>
 
 # Acknowledgments # {#acknowledgments}